src/java.net.http/share/classes/jdk/internal/net/http/websocket/MessageEncoder.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 package jdk.internal.net.http.websocket;

 import jdk.internal.net.http.common.Logger;
 import jdk.internal.net.http.common.Utils;
 import jdk.internal.net.http.websocket.Frame.Opcode;

 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.charset.CharacterCodingException;
 import java.nio.charset.CharsetEncoder;
 import java.nio.charset.CoderResult;
 import java.nio.charset.CodingErrorAction;
 import java.nio.charset.StandardCharsets;
 import java.security.SecureRandom;

 /*
  * A stateful producer of binary representations of WebSocket messages being
  * sent from the client to the server.
  *
  * An encoding method is given an original message and a byte buffer to put the
  * resulting bytes to. The method is called until it returns true. Then the
  * reset method is called. The whole sequence repeats with next message.
  */
 public class MessageEncoder {

     private static final Logger debug =
             Utils.getWebSocketLogger("[Output]"::toString, Utils.DEBUG_WS);

     private final SecureRandom maskingKeySource = new SecureRandom();
     private final Frame.HeaderWriter headerWriter = new Frame.HeaderWriter();
     private final Frame.Masker payloadMasker = new Frame.Masker();
     private final CharsetEncoder charsetEncoder
             = StandardCharsets.UTF_8.newEncoder()
                                     .onMalformedInput(CodingErrorAction.REPORT)
                                     .onUnmappableCharacter(CodingErrorAction.REPORT);
     /*
      * This buffer is used both to encode characters to UTF-8 and to calculate
      * the length of the resulting frame's payload. The length of the payload
      * must be known before the frame's header can be written.
      * For implementation reasons, this buffer must have a capacity of at least
      * the maximum size of a Close frame payload, which is 125 bytes
      * (or Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH).
      */
     private final ByteBuffer intermediateBuffer = createIntermediateBuffer(
             Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH);
     private final ByteBuffer headerBuffer = ByteBuffer.allocate(
             Frame.MAX_HEADER_SIZE_BYTES);

     private boolean started;
     private boolean flushing;
     private boolean moreText = true;
     private long headerCount;
     /* Has the previous frame got its fin flag set? */
     private boolean previousFin = true;
     /* Was the previous frame TEXT or a CONTINUATION thereof? */
     private boolean previousText;
     private boolean closed;

     /*
      * How many bytes of the current message have been already encoded.
      *
      * Even though the user hands their buffers over to us, they still can
      * manipulate these buffers while we are getting data out of them.
      * The number of produced bytes guards us from such behaviour in the
      * case of messages that must be restricted in size (Ping, Pong and Close).
      * For other messages this measure provides a best-effort attempt to detect
      * concurrent changes to buffer.
      *
      * Making a shallow copy (duplicate/slice) and then checking the size
      * precondition on it would also solve the problem, but at the cost of this
      * extra copy.
      */
     private int actualLen;

     /*
      * How many bytes were originally there in the message, before the encoding
      * started.
      */
     private int expectedLen;

     /* Exposed for testing purposes */
     protected ByteBuffer createIntermediateBuffer(int minSize) {
         int capacity = Utils.getIntegerNetProperty(
                 "jdk.httpclient.websocket.intermediateBufferSize", 16384);
         return ByteBuffer.allocate(Math.max(minSize, capacity));
     }

     public void reset() {
         // Do not reset the message stream state fields, e.g. previousFin,
         // previousText. Just an individual message state:
         started = false;
         flushing = false;
         moreText = true;
         headerCount = 0;
         actualLen = 0;
     }

     /*
      * Encodes text messages by cutting them into fragments of maximum size of
      * intermediateBuffer.capacity()
      */
     public boolean encodeText(CharBuffer src, boolean last, ByteBuffer dst)
             throws IOException
     {
         if (debug.on()) {
             debug.log("encode text src=[pos=%s lim=%s cap=%s] last=%s dst=%s",
                       src.position(), src.limit(), src.capacity(), last, dst);
         }
         if (closed) {
             throw new IOException("Output closed");
         }
         if (!started) {
             if (!previousText && !previousFin) {
                 // Previous data message was a partial binary message
                 throw new IllegalStateException("Unexpected text message");
             }
             started = true;
             headerBuffer.position(0).limit(0);
             intermediateBuffer.position(0).limit(0);
             charsetEncoder.reset();
         }
         while (true) {
             if (debug.on()) {
                 debug.log("put");
             }
             if (!putAvailable(headerBuffer, dst)) {
                 return false;
             }
             if (debug.on()) {
                 debug.log("mask");
             }
             if (maskAvailable(intermediateBuffer, dst) < 0) {
                 return false;
             }
             if (debug.on()) {
                 debug.log("moreText");
             }
             if (!moreText) {
                 previousFin = last;
                 previousText = true;
                 return true;
             }
             intermediateBuffer.clear();
             CoderResult r = null;
             if (!flushing) {
                 r = charsetEncoder.encode(src, intermediateBuffer, true);
                 if (r.isUnderflow()) {
                     flushing = true;
                 }
             }
             if (flushing) {
                 r = charsetEncoder.flush(intermediateBuffer);
                 if (r.isUnderflow()) {
                     moreText = false;
                 }
             }
             if (r.isError()) {
                 try {
                     r.throwException();
                 } catch (CharacterCodingException e) {
                     throw new IOException("Malformed text message", e);
                 }
             }
             if (debug.on()) {
                 debug.log("frame #%s", headerCount);
             }
             intermediateBuffer.flip();
             Opcode opcode = previousFin && headerCount == 0
                     ? Opcode.TEXT : Opcode.CONTINUATION;
             boolean fin = last && !moreText;
             setupHeader(opcode, fin, intermediateBuffer.remaining());
             headerCount++;
         }
     }

     private boolean putAvailable(ByteBuffer src, ByteBuffer dst) {
         int available = dst.remaining();
         if (available >= src.remaining()) {
             dst.put(src);
             return true;
         } else {
             int lim = src.limit();                   // save the limit
             src.limit(src.position() + available);
             dst.put(src);
             src.limit(lim);                          // restore the limit
             return false;
         }
     }

     public boolean encodeBinary(ByteBuffer src, boolean last, ByteBuffer dst)
             throws IOException
     {
         if (debug.on()) {
             debug.log("encode binary src=%s last=%s dst=%s",
                       src, last, dst);
         }
         if (closed) {
             throw new IOException("Output closed");
         }
         if (!started) {
             if (previousText && !previousFin) {
                 // Previous data message was a partial text message
                 throw new IllegalStateException("Unexpected binary message");
             }
             expectedLen = src.remaining();
             Opcode opcode = previousFin ? Opcode.BINARY : Opcode.CONTINUATION;
             setupHeader(opcode, last, expectedLen);
             previousFin = last;
             previousText = false;
             started = true;
         }
         if (!putAvailable(headerBuffer, dst)) {
             return false;
         }
         int count = maskAvailable(src, dst);
         actualLen += Math.abs(count);
         if (count >= 0 && actualLen != expectedLen) {
             throw new IOException("Concurrent message modification");
         }
         return count >= 0;
     }

     private int maskAvailable(ByteBuffer src, ByteBuffer dst) {
         int r0 = dst.remaining();
         payloadMasker.transferMasking(src, dst);
         int masked = r0 - dst.remaining();
         return src.hasRemaining() ? -masked : masked;
     }

     public boolean encodePing(ByteBuffer src, ByteBuffer dst)
             throws IOException
     {
         if (debug.on()) {
             debug.log("encode ping src=%s dst=%s", src, dst);
         }
         if (closed) {
             throw new IOException("Output closed");
         }
         if (!started) {
             expectedLen = src.remaining();
             if (expectedLen > Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH) {
                 throw new IllegalArgumentException("Long message: " + expectedLen);
             }
             setupHeader(Opcode.PING, true, expectedLen);
             started = true;
         }
         if (!putAvailable(headerBuffer, dst)) {
             return false;
         }
         int count = maskAvailable(src, dst);
         actualLen += Math.abs(count);
         if (count >= 0 && actualLen != expectedLen) {
             throw new IOException("Concurrent message modification");
         }
         return count >= 0;
     }

     public boolean encodePong(ByteBuffer src, ByteBuffer dst)
             throws IOException
     {
         if (debug.on()) {
             debug.log("encode pong src=%s dst=%s",
                       src, dst);
         }
         if (closed) {
             throw new IOException("Output closed");
         }
         if (!started) {
             expectedLen = src.remaining();
             if (expectedLen > Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH) {
                 throw new IllegalArgumentException("Long message: " + expectedLen);
             }
             setupHeader(Opcode.PONG, true, expectedLen);
             started = true;
         }
         if (!putAvailable(headerBuffer, dst)) {
             return false;
         }
         int count = maskAvailable(src, dst);
         actualLen += Math.abs(count);
         if (count >= 0 && actualLen != expectedLen) {
             throw new IOException("Concurrent message modification");
         }
         return count >= 0;
     }

     public boolean encodeClose(int statusCode, CharBuffer reason, ByteBuffer dst)
             throws IOException
     {
         if (debug.on()) {
             debug.log("encode close statusCode=%s reason=[pos=%s lim=%s cap=%s] dst=%s",
                       statusCode, reason.position(), reason.limit(), reason.capacity(), dst);
         }
         if (closed) {
             throw new IOException("Output closed");
         }
         if (!started) {
             if (debug.on()) {
                 debug.log("reason [pos=%s lim=%s cap=%s]",
                           reason.position(), reason.limit(), reason.capacity());
             }
             intermediateBuffer.position(0).limit(Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH);
             intermediateBuffer.putChar((char) statusCode);
             CoderResult r = charsetEncoder.reset().encode(reason, intermediateBuffer, true);
             if (r.isUnderflow()) {
                 if (debug.on()) {
                     debug.log("flushing");
                 }
                 r = charsetEncoder.flush(intermediateBuffer);
             }
             if (debug.on()) {
                 debug.log("encoding result: %s", r);
             }
             if (r.isError()) {
                 try {
                     r.throwException();
                 } catch (CharacterCodingException e) {
                     throw new IOException("Malformed reason", e);
                 }
             } else if (r.isOverflow()) {
                 // Here the 125 bytes size is ensured by the check for overflow
                 throw new IOException("Long reason");
             } else if (!r.isUnderflow()) {
                 throw new InternalError(); // assertion
             }
             intermediateBuffer.flip();
             setupHeader(Opcode.CLOSE, true, intermediateBuffer.remaining());
             started = true;
             closed = true;
             if (debug.on()) {
                 debug.log("intermediateBuffer=%s", intermediateBuffer);
             }
         }
         if (!putAvailable(headerBuffer, dst)) {
             return false;
         }
         return maskAvailable(intermediateBuffer, dst) >= 0;
     }

     private void setupHeader(Opcode opcode, boolean fin, long payloadLen) {
         if (debug.on()) {
             debug.log("frame opcode=%s fin=%s len=%s",
                       opcode, fin, payloadLen);
         }
         headerBuffer.clear();
         int mask = maskingKeySource.nextInt();
         headerWriter.fin(fin)
                     .opcode(opcode)
                     .payloadLen(payloadLen)
                     .mask(mask)
                     .write(headerBuffer);
         headerBuffer.flip();
         payloadMasker.mask(mask);
     }
 }
	/*
	* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.internal.net.http.websocket;

	import jdk.internal.net.http.common.Logger;
	import jdk.internal.net.http.common.Utils;
	import jdk.internal.net.http.websocket.Frame.Opcode;

	import java.io.IOException;
	import java.nio.ByteBuffer;
	import java.nio.CharBuffer;
	import java.nio.charset.CharacterCodingException;
	import java.nio.charset.CharsetEncoder;
	import java.nio.charset.CoderResult;
	import java.nio.charset.CodingErrorAction;
	import java.nio.charset.StandardCharsets;
	import java.security.SecureRandom;

	/*
	* A stateful producer of binary representations of WebSocket messages being
	* sent from the client to the server.
	*
	* An encoding method is given an original message and a byte buffer to put the
	* resulting bytes to. The method is called until it returns true. Then the
	* reset method is called. The whole sequence repeats with next message.
	*/
	public class MessageEncoder {

	private static final Logger debug =
	Utils.getWebSocketLogger("[Output]"::toString, Utils.DEBUG_WS);

	private final SecureRandom maskingKeySource = new SecureRandom();
	private final Frame.HeaderWriter headerWriter = new Frame.HeaderWriter();
	private final Frame.Masker payloadMasker = new Frame.Masker();
	private final CharsetEncoder charsetEncoder
	= StandardCharsets.UTF_8.newEncoder()
	.onMalformedInput(CodingErrorAction.REPORT)
	.onUnmappableCharacter(CodingErrorAction.REPORT);
	/*
	* This buffer is used both to encode characters to UTF-8 and to calculate
	* the length of the resulting frame's payload. The length of the payload
	* must be known before the frame's header can be written.
	* For implementation reasons, this buffer must have a capacity of at least
	* the maximum size of a Close frame payload, which is 125 bytes
	* (or Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH).
	*/
	private final ByteBuffer intermediateBuffer = createIntermediateBuffer(
	Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH);
	private final ByteBuffer headerBuffer = ByteBuffer.allocate(
	Frame.MAX_HEADER_SIZE_BYTES);

	private boolean started;
	private boolean flushing;
	private boolean moreText = true;
	private long headerCount;
	/* Has the previous frame got its fin flag set? */
	private boolean previousFin = true;
	/* Was the previous frame TEXT or a CONTINUATION thereof? */
	private boolean previousText;
	private boolean closed;

	/*
	* How many bytes of the current message have been already encoded.
	*
	* Even though the user hands their buffers over to us, they still can
	* manipulate these buffers while we are getting data out of them.
	* The number of produced bytes guards us from such behaviour in the
	* case of messages that must be restricted in size (Ping, Pong and Close).
	* For other messages this measure provides a best-effort attempt to detect
	* concurrent changes to buffer.
	*
	* Making a shallow copy (duplicate/slice) and then checking the size
	* precondition on it would also solve the problem, but at the cost of this
	* extra copy.
	*/
	private int actualLen;

	/*
	* How many bytes were originally there in the message, before the encoding
	* started.
	*/
	private int expectedLen;

	/* Exposed for testing purposes */
	protected ByteBuffer createIntermediateBuffer(int minSize) {
	int capacity = Utils.getIntegerNetProperty(
	"jdk.httpclient.websocket.intermediateBufferSize", 16384);
	return ByteBuffer.allocate(Math.max(minSize, capacity));
	}

	public void reset() {
	// Do not reset the message stream state fields, e.g. previousFin,
	// previousText. Just an individual message state:
	started = false;
	flushing = false;
	moreText = true;
	headerCount = 0;
	actualLen = 0;
	}

	/*
	* Encodes text messages by cutting them into fragments of maximum size of
	* intermediateBuffer.capacity()
	*/
	public boolean encodeText(CharBuffer src, boolean last, ByteBuffer dst)
	throws IOException
	{
	if (debug.on()) {
	debug.log("encode text src=[pos=%s lim=%s cap=%s] last=%s dst=%s",
	src.position(), src.limit(), src.capacity(), last, dst);
	}
	if (closed) {
	throw new IOException("Output closed");
	}
	if (!started) {
	if (!previousText && !previousFin) {
	// Previous data message was a partial binary message
	throw new IllegalStateException("Unexpected text message");
	}
	started = true;
	headerBuffer.position(0).limit(0);
	intermediateBuffer.position(0).limit(0);
	charsetEncoder.reset();
	}
	while (true) {
	if (debug.on()) {
	debug.log("put");
	}
	if (!putAvailable(headerBuffer, dst)) {
	return false;
	}
	if (debug.on()) {
	debug.log("mask");
	}
	if (maskAvailable(intermediateBuffer, dst) < 0) {
	return false;
	}
	if (debug.on()) {
	debug.log("moreText");
	}
	if (!moreText) {
	previousFin = last;
	previousText = true;
	return true;
	}
	intermediateBuffer.clear();
	CoderResult r = null;
	if (!flushing) {
	r = charsetEncoder.encode(src, intermediateBuffer, true);
	if (r.isUnderflow()) {
	flushing = true;
	}
	}
	if (flushing) {
	r = charsetEncoder.flush(intermediateBuffer);
	if (r.isUnderflow()) {
	moreText = false;
	}
	}
	if (r.isError()) {
	try {
	r.throwException();
	} catch (CharacterCodingException e) {
	throw new IOException("Malformed text message", e);
	}
	}
	if (debug.on()) {
	debug.log("frame #%s", headerCount);
	}
	intermediateBuffer.flip();
	Opcode opcode = previousFin && headerCount == 0
	? Opcode.TEXT : Opcode.CONTINUATION;
	boolean fin = last && !moreText;
	setupHeader(opcode, fin, intermediateBuffer.remaining());
	headerCount++;
	}
	}

	private boolean putAvailable(ByteBuffer src, ByteBuffer dst) {
	int available = dst.remaining();
	if (available >= src.remaining()) {
	dst.put(src);
	return true;
	} else {
	int lim = src.limit(); // save the limit
	src.limit(src.position() + available);
	dst.put(src);
	src.limit(lim); // restore the limit
	return false;
	}
	}

	public boolean encodeBinary(ByteBuffer src, boolean last, ByteBuffer dst)
	throws IOException
	{
	if (debug.on()) {
	debug.log("encode binary src=%s last=%s dst=%s",
	src, last, dst);
	}
	if (closed) {
	throw new IOException("Output closed");
	}
	if (!started) {
	if (previousText && !previousFin) {
	// Previous data message was a partial text message
	throw new IllegalStateException("Unexpected binary message");
	}
	expectedLen = src.remaining();
	Opcode opcode = previousFin ? Opcode.BINARY : Opcode.CONTINUATION;
	setupHeader(opcode, last, expectedLen);
	previousFin = last;
	previousText = false;
	started = true;
	}
	if (!putAvailable(headerBuffer, dst)) {
	return false;
	}
	int count = maskAvailable(src, dst);
	actualLen += Math.abs(count);
	if (count >= 0 && actualLen != expectedLen) {
	throw new IOException("Concurrent message modification");
	}
	return count >= 0;
	}

	private int maskAvailable(ByteBuffer src, ByteBuffer dst) {
	int r0 = dst.remaining();
	payloadMasker.transferMasking(src, dst);
	int masked = r0 - dst.remaining();
	return src.hasRemaining() ? -masked : masked;
	}

	public boolean encodePing(ByteBuffer src, ByteBuffer dst)
	throws IOException
	{
	if (debug.on()) {
	debug.log("encode ping src=%s dst=%s", src, dst);
	}
	if (closed) {
	throw new IOException("Output closed");
	}
	if (!started) {
	expectedLen = src.remaining();
	if (expectedLen > Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH) {
	throw new IllegalArgumentException("Long message: " + expectedLen);
	}
	setupHeader(Opcode.PING, true, expectedLen);
	started = true;
	}
	if (!putAvailable(headerBuffer, dst)) {
	return false;
	}
	int count = maskAvailable(src, dst);
	actualLen += Math.abs(count);
	if (count >= 0 && actualLen != expectedLen) {
	throw new IOException("Concurrent message modification");
	}
	return count >= 0;
	}

	public boolean encodePong(ByteBuffer src, ByteBuffer dst)
	throws IOException
	{
	if (debug.on()) {
	debug.log("encode pong src=%s dst=%s",
	src, dst);
	}
	if (closed) {
	throw new IOException("Output closed");
	}
	if (!started) {
	expectedLen = src.remaining();
	if (expectedLen > Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH) {
	throw new IllegalArgumentException("Long message: " + expectedLen);
	}
	setupHeader(Opcode.PONG, true, expectedLen);
	started = true;
	}
	if (!putAvailable(headerBuffer, dst)) {
	return false;
	}
	int count = maskAvailable(src, dst);
	actualLen += Math.abs(count);
	if (count >= 0 && actualLen != expectedLen) {
	throw new IOException("Concurrent message modification");
	}
	return count >= 0;
	}

	public boolean encodeClose(int statusCode, CharBuffer reason, ByteBuffer dst)
	throws IOException
	{
	if (debug.on()) {
	debug.log("encode close statusCode=%s reason=[pos=%s lim=%s cap=%s] dst=%s",
	statusCode, reason.position(), reason.limit(), reason.capacity(), dst);
	}
	if (closed) {
	throw new IOException("Output closed");
	}
	if (!started) {
	if (debug.on()) {
	debug.log("reason [pos=%s lim=%s cap=%s]",
	reason.position(), reason.limit(), reason.capacity());
	}
	intermediateBuffer.position(0).limit(Frame.MAX_CONTROL_FRAME_PAYLOAD_LENGTH);
	intermediateBuffer.putChar((char) statusCode);
	CoderResult r = charsetEncoder.reset().encode(reason, intermediateBuffer, true);
	if (r.isUnderflow()) {
	if (debug.on()) {
	debug.log("flushing");
	}
	r = charsetEncoder.flush(intermediateBuffer);
	}
	if (debug.on()) {
	debug.log("encoding result: %s", r);
	}
	if (r.isError()) {
	try {
	r.throwException();
	} catch (CharacterCodingException e) {
	throw new IOException("Malformed reason", e);
	}
	} else if (r.isOverflow()) {
	// Here the 125 bytes size is ensured by the check for overflow
	throw new IOException("Long reason");
	} else if (!r.isUnderflow()) {
	throw new InternalError(); // assertion
	}
	intermediateBuffer.flip();
	setupHeader(Opcode.CLOSE, true, intermediateBuffer.remaining());
	started = true;
	closed = true;
	if (debug.on()) {
	debug.log("intermediateBuffer=%s", intermediateBuffer);
	}
	}
	if (!putAvailable(headerBuffer, dst)) {
	return false;
	}
	return maskAvailable(intermediateBuffer, dst) >= 0;
	}

	private void setupHeader(Opcode opcode, boolean fin, long payloadLen) {
	if (debug.on()) {
	debug.log("frame opcode=%s fin=%s len=%s",
	opcode, fin, payloadLen);
	}
	headerBuffer.clear();
	int mask = maskingKeySource.nextInt();
	headerWriter.fin(fin)
	.opcode(opcode)
	.payloadLen(payloadLen)
	.mask(mask)
	.write(headerBuffer);
	headerBuffer.flip();
	payloadMasker.mask(mask);
	}
	}